1. Field of the Invention
This invention relates to a storing device for an easily polymerizable and/or coagulating liquid substance and a method for the control of pressure in the device.
2. Description of Related Art
The interior of a tank containing a polymerizable or coagulating liquid is generally retained under prescribed pressure. When the interior pressure of this tank tends to increase or decrease from the prescribed pressure, the breather valve opens and adjusts the pressure with a view to preventing the tank from being deformed or fractured.
For tanks that are sealed with a gas, a method is widely adopted which comprising introducing a gas by a PC (Pressure Control) valve and, when the gas pressure in the tank becomes unduly high, causing this inner pressure to revert to the fixed level by discharging the excess of the gas by a breather valve or a pressure seal pot as the method for retaining the inner pressure of a pressured tank. The atmospheric storage tanks generally adopt the method which comprises retaining the inner pressure of a tank (atmospheric pressure) by exposing the interior of the tank to atmosphere through a vent line disposed in the tank and allowing the tank to acquire a necessary gas seal by the supply of a gas at a fixed flow volume by a FC (Flow Control) valve.
In tanks for storing an easily polymerizable or coagulating compound, however, polymerization or condensation occurs in the gas phase part of the tanks and a polymer or a condensate adheres to the roof part of the tanks. In other words, the breather valve, the PC valve, and the vent line of the tank incur blockage due to the adhesion of the polymer or condensate and then they permit admission or release of a gas therethrough only with difficulty.
On the blockage mentioned above occurs, when the inner pressure of the tank rises, it is impossible for the gas to be discharged through the breather valve or the vent line and inflicts deformation or fracture on the tank. Conversely, the tank possibly sustains deformation such as depression or fracture during the presence of decompression, since the gas introduction through the breather valve or the vent line is not attainable.
When the interior of tanks is capable of repressing polymerization or condensation, it can preclude the blockage in the valve, the breather valve, and the vent line and adjust the pressure. The repression of polymerization in the tank may be accomplished by the method that comprises circulating a liquid in the tank and adding a polymerization inhibitor such as hydroquinone or phenothiazine to therein. The inhibitor is present mainly in the liquid phase and nearly absent in the gas phase. When the vapor condenses on the dry part of tank interior, it readily polymerizes and comes to clog the pipings to the tank because the inhibitor is scarce in the gas phase.
Thus, the conventional method possibly entails the problem of suffering a decrease in productivity (storing property) in the tank for storing an easily polymerizable substance and fails to permit safe lasting storage of the substance.
It is, therefore, an object of this invention to provide a tank which serves to admit and emit a polymerizable or coagulating liquid, is capable of preventing the tank from being deformed and fractured by the phenomenon of compression and decompression, and is enhanced safety of operation.
Another object of the invention is to provide a method for preventing a storing device from inducing polymerization of the substance being stored therein and enabling this device to acquire high productivity.
We have pursued a diligent study concerning a tank serving to admit and emit a polymerizable or coagulating liquid, and found that by providing a gas-sealing device and/or a heating device in the pipe between a liquid sealing device and the tank with, it is possible to prevent polymerization of the polymerizable substance, prevent the pipe from being blocked, and consequently prevent the tank from being deformed or fractured. This invention has been perfected.
The object of this invention is accomplished by a storing device characterized by providing a gas-sealing device and/or a heating device in the pipe between a storing tank for an easily polymerizable and/or coagulating liquid substance and a liquid sealing implement-protecting device.
The object of this invention is also accomplished by a method for controlling the pressure of a storing device, characterized by flowing a sealing gas in the pipe between a storing tank for an easily polymerizable and/or coagulating liquid substance and a liquid sealing implement-protecting device and/or heating the pipe.
According to the storing device of the invention, since providing the gas-sealing device or the heating device or optionally both for the pipe between the tank and the liquid sealing implement-protecting device, it is incapable of condensing within the pipe the vapor generated from the liquid in the tank and, further because of the continued flow of the sealing gas within the pipe, is capable of precluding the possible stagnation of the vapor in the pipe, allaying or eliminating the condensation and polymerization of the vapor, and consequently preventing the tank from being deformed or fractured.
According to the method for controlling the inner pressure of the storing device of the invention, by a simple procedure of continuously flowing a sealing gas to the pipe between a tank and a liquid sealing implement-protecting device or heating the pipe or optionally performing both these actions, it is enabled to allay or eliminate the adhesion to the pipe of the vapor generated from the liquid and consequently prevent the tank from being deformed or fractured.
The above and other objects, features and advantages of the present invention will become clear from the following description of the preferred embodiments.